Non-impact keyless chuck

ABSTRACT

A non-impact keyless chuck suitable for use with manual or powered drivers is disclosed. The chuck comprises a body which carries a rotatable split nut having a relatively fine thread and a plurality of slidable jaws, which may be identical, driven by the rotatable nut. An anti-friction bearing is disposed between the rotatable nut and a bearing thrust ring mounted on the body. A clutch or torque limiting mechanism is provided to limit the tightening torque to a predetermined value while the loosening torque may be limited or unlimited. The front sleeve, and rear sleeve, if used, may be formed from a structural plastic to reduce manufacturing costs. A relatively soft elastomeric grip boot may be placed on the front sleeve to improve the grip and temporarily restrain and center the tool during chuck tightening or loosening operations. A relatively soft elastomeric grip boot may also be placed on the rear sleeve, if used.

CLAIM OF PRIORITY

[0001] The present application is a continuation of application Ser. No.09/954,829, filed Sep. 12, 2001, which is a continuation of applicationSer. No. 09/570,427, filed May 12, 2000, now U.S. Pat. No. 6,296,257,which is a continuation of application Ser. No. 09/329,700, filed Jun.10, 1999, now U.S. Pat. No. 6,286,842, which is a continuation ofapplication Ser. No. 08/704,418, filed Aug. 20, 1996, now U.S. Pat. No.5,924,702, which is a continuation of application Ser. No. 08/476,896,filed Jun. 7, 1995, now U.S. Pat. No. 5,573,254, which is a continuationof application Ser. No. 08/322,356, filed Oct. 13, 1994, now U.S. Pat.No. 5,452,906, which is a continuation of application 08/234,227, filedApr. 28, 1994, now abandoned, which is a continuation of application08/099,160, filed Jul. 29, 1993, now U.S. Pat. No. 5,330,204, which is acontinuation of application Ser. No. 07/884,205, filed May 18, 1992, nowU.S. Pat. No. 5,253,879, which is a division of application Ser. No.07/449,722, filed Dec. 11, 1989, now U.S. Pat. No. 5,125,673, the entiredisclosure of each hereby being incorporated by reference in theirentirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention relates to drill chucks for use with hand drillsor with electric or pneumatic power drivers. More particularly, itrelates to a chuck of the keyless type which may be tightened orloosened by hand or by actuation of the driver motor.

[0004] 2. Prior Art

[0005] Both hand and electric or pneumatic tool drivers are well known.Although twist drills are the most common tools used with such drivers,the tools may also comprise screw drivers, nut drivers, burrs, mountedgrinding stones and other cutting or abrading tools. Since the tools mayhave shanks of varying diameter or the cross-section of the tool shankmay be polygonal, the device is usually provided with a chuck which isadjustable over a relatively wide range. The chuck may be attached tothe driver by a threaded or tapered bore.

[0006] A wide variety of chucks has been developed by the art. In thesimplest form of chuck, three jaws spaced circumferentially 120 degreeapart from each other are constrained by a conical body threaded ontothe drive shaft so that rotation of the body in one direction relativeto the drive shaft forces the jaws into gripping relationship withrespect to the cylindrical shank of a tool while rotation in theopposite direction releases the gripping relationship. Such a chuck maybe keyless if the body is rotated by hand. However, because thetightening or loosening torque which may be applied directly in a handoperation is limited, the art developed the so-called three-jaw gearedchuck. This design overcomes the principal problems in the earlierdesign by providing guideways in the chuck body to control moreaccurately the motion of the jaws and teeth on the jaws which mesh witha gear driven nut mounted on the chuck body. The gear is actuated by apinion formed on a separate key which may be rotated in a bearing holeformed in the chuck body.

[0007] The three-jaw geared chuck is, or can be, a high qualityprecision tool which can exert a relatively large gripping force on thetool. However, the separate key may easily be misplaced or accidentallyleft in the chuck when the driver is actuated, thus possibly leading tosome personal injury. In addition, the chucking or unchucking operationis a two-handed procedure which is time consuming.

[0008] To overcome these perceived disadvantages of the key operatedgear chuck, various keyless chucks have now been developed. Such keylesschucks fall broadly into two classes: impact and non-impact chucks.Impact chucks employ means to apply a series of impacts to the nut so asto tighten or loosen the jaws. In the non-impact design, manual ormechanical means are used to restrain one member of the chuck while atorque is applied to another member of the chuck either manually or bythe power driver to move the nut relative to the jaws. A keyless chuckof the impact type is disclosed in McCarthy U.S. Pat. No. 4,840,387while the prior art cited therein illustrates keyless chucks both of theimpact and the non-impact variety.

SUMMARY OF THE INVENTION

[0009] In accordance with the present invention, a keyless chuck of thenon-impact type is provided. The invention employs an anti-frictionbearing interposed between the nut and the body to decrease the frictionlosses in the mechanism so as to increase the effective tighteningtorque. The bearing thrust ring is formed separately from the bodymember and pressed thereon so as to increase the effective diameter ofthe body while minimizing the machining requirements. The principalload-bearing parts of the chuck, i.e., the jaws, body, nut, bearing andbearing race are formed from metal while the front and back sleeves andrelated parts may be formed from plastic materials so as to reduce thecost and permit customizing of the chuck.

[0010] Additional features of the invention include an elastomeric gripboot for the front sleeve which also functions as a bit holder andcentering device, a one-way torque limiting clutch for limiting thetightening torque while permitting positive loosening torque, and atorque-limiting clutch which provides greater loosening torque thantightening torque. In accordance with a process feature of theinvention, the three jaws are identical with respect to their nutengaging threads and the eccentricity of their engagement is overcome bya grinding procedure following assembly of the chuck.

DESCRIPTION OF THE DRAWINGS

[0011] Further objects and advantages of the invention will becomeapparent from the following detailed description and the accompanyingdrawings in which:

[0012]FIG. 1 is a perspective view of a keyless chuck in accordance withthe present invention,

[0013]FIG. 2 is an enlarged longitudinal view, partly in section takenalong line 2--2 of FIG. 1,

[0014]FIG. 3 is a transverse cross-sectional view taken along line 3--3of FIG. 2,

[0015]FIG. 4 is an enlarged longitudinal view, partly in section, of analternative form of the invention including a torque limiting mechanismand a bit retaining and centering device,

[0016]FIG. 5 is a transverse cross-sectional view taken along 5--5 ofFIG. 4 and showing the torque limiting mechanism,

[0017]FIG. 5A is a fragmentary cross-sectional view showing analternative form of the torque limiting mechanism,

[0018]FIG. 5B is a fragmentary cross-sectional view showing analternative form of the torque limiting mechanism,

[0019]FIG. 5C is a fragmentary cross-sectional view showing analternative form of the torque limiting mechanism,

[0020]FIG. 5D is a fragmentary cross-sectional view showing analternative form of the torque limiting mechanism,

[0021]Fig. 5E is a fragmentary cross-sectional view showing analternative form of the torque limiting mechanism,

[0022]Fig. 5F is a fragmentary cross-sectional view showing analternative form of the torque limiting mechanism,

[0023]FIG. 5G is a fragmentary cross-sectional view showing analternative form of the torque limiting mechanism,

[0024]FIG. 6A is a plan view of a toothed retainer disc shown in FIG. 4,

[0025]FIG. 6B is an edge view, of the retainer disc shown in FIG. 6A,

[0026]FIG. 6C is an edge view, partly in section, of an alternative formof the retainer disc having a beveled rim,

[0027]FIG. 6D is a plan view of a toothless retainer disc having abeveled rim,

[0028]FIG. 6E is an edge view, partly in section, of the retainer discshown in FIG. 6D,

[0029]FIG. 7 is an enlarged longitudinal view, partly in section, of afurther alternative form of the invention which is particularly adaptedfor manual operation,

[0030]FIG. 8 is a fragmentary view taken along line 8--8 of FIG. 7 andshowing the clutch mechanism.

DETAILED DESCRIPTION OF THE INVENTION

[0031] Referring now to FIG. 1, there is illustrated a chuck 10 inaccordance with the present invention. The chuck 10 includes a frontsleeve member 12, an optional rear sleeve member 14, a body member 16and jaws 18.

[0032] As shown more clearly in FIG. 2, the body member 16 is generallycylindrical in shape and comprises a nose or forward section 20 and atail or rearward section 22. The nose section 20 is, preferably,chamfered at its outer end. An axial bore 24 is formed in the nosesection 20 of the body member 16. Axial bore 24 is somewhat larger thanthe largest tool shank which the chuck is designed to accommodate. Athreaded bore 26 is formed in the tail section 22 of the body 16 and isof a standard size to mate with the threaded drive shaft of a powered orhand driver (not shown). The bores 24, 26 may communicate at the centralregion 28 of the body member 16. If desired, the threaded bore 26 may bereplaced by a tapered, unthreaded bore of a standard size to mate with atapered drive shaft.

[0033] Passageways 30 are formed in the body member 16 to accommodateeach jaw 18. Preferably, three jaws 18 are employed and each jaw 18 isseparated from the adjacent jaw by an arc of 120 degree. The axes of thepassageways 30 and the jaws 18 are angled with respect to the chuck axisbut intersect the chuck axis at a common point ahead of the chuck body16. Each jaw 18 has a tool engaging face 32 which is generally parallelto the axis of the chuck body 16 and threads 34 on its opposite or outersurface. In accordance with a feature of the present invention, thethreads 34 have a relatively fine pitch, i.e., a pitch greater than 20threads per inch, e.g., 32 threads per inch, and the threads,preferably, are of the buttress type though other thread forms may beemployed. By employing the buttress thread form the tightening forceapplied to the jaw threads 34 is substantially axial to the jaw 18 so asto maximize the conversion of the tightening torque applied to the chuckinto a gripping force applied to the tool shank. The use of a relativelyfine pitch thread results in two advantages for the chuck in accordancewith the present invention. First, the relatively fine pitch results ina greater mechanical advantage so that a given tightening torque isconverted into a larger gripping force. Second, it becomes possible touse interchangeable jaws 18 of identical design rather than slightlydifferent jaws that must be selected and assembled as a set. The smalleccentricity which results from the use of identical jaw pieces inaccordance with the present invention can be counteracted by a grindingstep as more fully described below.

[0034] A circumferential groove 36 is formed in the body member 16 andextends into the passageways 30. A split nut 38 having female threads 40is located in the circumferential groove 36 and secured therein by thefront sleeve member 12. The split nut 38 is preferably formed withcircumferential serrations or teeth 44 and the outer edges are providedwith a small chamfer to facilitate press fitting of the split nut 38into the bore 42 of the front sleeve 12. Preferably, the front sleeve isformed from a structural plastic such as a polycarbonate, a filledpolypropylene, e.g., glass-filled polypropylene, or a blend ofstructural plastic materials. The serrations or teeth on the split nut38 assure that the front sleeve 12 will hold the split nut 38 securelywithout being subjected to an excessive hoop stress.

[0035] A circumferential race 46, which may be grooved or a flatsurface, is formed on the rear face of split nut 38 to accommodate ananti-friction bearing, for example, ball bearing assembly 48. Ifdesired, the bearing assembly 48 may include a bearing retainer 49 (seeFIG. 4) which locates the plurality of balls while permitting them toroll. A bearing thrust ring 50 is provided with a central hole 52 sizedto be press fitted on the body member 16. One face of the bearing thrustring 50 has formed thereon a bearing race 54, which may be grooved orflat, against which the bearing assembly 48 rides. A plurality of jawguideways 56 are formed around the circumference of the central hole 52in the thrust ring 50 to permit the retraction of the jaws 18therethrough. The guideways are shaped to conform with the toothed areaof the jaws 18 so as to reduce or prevent toggling of the jaws 18. Toperform this function, the axial length of the guideways 56 must begreater than the pitch of the threads 34 on the jaws 18. The outercircumference of the bearing thrust ring 50 may have formed thereonserrations or teeth 58 and the outer edges may be chamfered so as tofacilitate pressing of the bearing thrust ring 50 into a bore 60 formedin the rear sleeve member 14. The rear sleeve member 14 also contains abore 62 adapted to mate with the tail section 22 of the body member 16.If desired, the rear sleeve member 14 may be omitted and the front,sleeve member 12 extended to the tail end of the body 16. Thisalternative is feasible when a spindle lock is provided on the driver orwhen the driver is used to tighten or loosen the jaws.

[0036] The circumferential surface of the front sleeve member 12 may beknurled as suggested at 63 or may be provided with longitudinal ribs orother protrusions to enable the operator to grip it securely. In likemanner, the circumferential surface of the rear sleeve member 14, ifemployed, may be knurled or ribbed, if desired.

[0037] It will be appreciated that the rear sleeve member 14 is fixed tothe body member 16 while the front sleeve member 12 is fixed to thesplit nut 38. Thus, relative movement of the front and rear sleevemembers 12, 14 will cause the jaws 18 to be advanced or retracted,depending upon the direction of the relative motion. As the bearing 48is interposed between the relatively moving parts, the frictional lossesare minimized and a maximum portion of the applied tightening torque isconverted to a tightening force on the tool shank. While the chuck, ofFIGS. 2 and 3 may be operated manually, it may also be operated by thepower driver.

[0038] As noted above, the jaws 18 are preferably formed so as to beidentical to each other. In threejaw geared chucks, it is commonpractice to offset the threads proportional to the thread pitch so thatwhen the jaws contact each other they will meet on the axis of thechuck. By making the jaws identical a degree of eccentricity will resultbut this is minimized by the fine pitch of the threads. In accordancewith the present invention, a grinding procedure may be performed afterthe chuck is assembled to remove the eccentricity resulting from thesmall axial displacement of the jaws relative to each other. When theeccentricity is removed, the centering accuracy of the chuck will be thesame as if custom sets of jaws had been provided.

[0039] Reference is now made to FIGS. 4 and 5 which illustrate analternative form of the present invention containing a torque limitingmechanism and a bit holding and centering device. Parts which aresubstantially the same as in the embodiment shown in FIGS. 2 and 3 areidentified by the same designators while modified parts are designatedwith the additional letter “a.”

[0040] In the embodiment shown in FIGS. 4 and 5 a torque limitingmechanism is provided which produces an audible “click” when the chuckhas attained its maximum tightness. This may be accomplished byproviding a toothed annulus 64 having a bore 66 which engages theoutside diameter of, or the teeth or serrations 44 on, the split nut 38so as to lock the split nut 38 in place. A series of flexible teeth 68are formed on the circumference of the annulus 64 which engage ribs 70formed on the lateral surface of a bore 72 in the front sleeve member 12a. As most clearly shown in FIG. 5 the flexible teeth 68 have a slopingforward edge 68 a which engages the ribs 70 during tightening of thechuck. When a predetermined tightening torque is reached, the ribs 70pass over the flexible teeth 68 producing an audible “click.” However,when the front sleeve 12 a is turned so as to loosen the chuck jaws 18,the ribs 70 lock with the teeth 68 to transfer all the applied torque tothe split nut 38.

[0041] It will be noted that the front sleeve 12 a extends beyond thenose 20 of the body member 16 to the region where the jaws 18 meet intheir fully closed position. A grip boot 74 may be fastened to the frontsleeve 12 a by ribs 76, 78 and prevented from turning relative to thefront sleeve 12 a by longitudinal ribs (not shown). The grip boot 74 ispreferably made from an elastomeric material such as natural orsynthetic rubber and has a relatively small flexible orifice 80 alignedwith the axis of the chuck body member 16. Preferably, the grip boot 74is made from a relatively soft material having a Shore A hardness offrom 40 to 70. The orifice 80 is sized so that it will stretch to gripthe shank of a drill or other tool inserted in the chuck and temporarilycenter and restrain the tool during chucking or unchucking operations.

[0042] In the embodiment of the invention shown in FIGS. 2 and 3, thefront sleeve 12 is held in place because it is press fitted to the splitnut 38. In the embodiment shown in FIGS. 4 and 5 other means arerequired to locate the front sleeve 12 a. A circumferential groove 82 isformed in the nose section 20 of the body member 16 to receive aretainer disc 84 which is pressed into the bore 72 of the front sleeve12 a. FIG. 6A shows a plan view of the retainer disc 84 havingcircumferential teeth 86 and flexible engaging tabs 88 formed by aseries of slots 90 stamped in the disc 84 around its center hole 92. Asshown in FIG. 6B, the retainer disc 84 is flat and relatively thin so asto enable it to be pressed on to the body member 16 and turn freely inthe groove 82. The retainer disc 84 is sized so that the teeth 86 firmlygrip the bore 72 of the front sleeve member 12 a. FIG. 6C illustrates analternative form of a toothed retainer disc 84 c having a beveled rim94. FIG. 6D shows a toothless retainer disc 84 d in plan view. Like thetoothed retainer disc 84, the center hole 92 has slots 90 formed aroundits edge to define flexible engaging tabs 88. FIG. 6E shows the beveledrim 96 which forms a deformable gripping member.

[0043] As noted above with reference to FIG. 5, the toothed annulus 64performs two functions: first, it holds the split nut 38 in place, and,second, it forms one part of the torque limiting mechanism. FIGS. 5A-5Gillustrate a number of alternative designs for the toothed annulus 64.In FIG. 5A the annulus 64 a is formed with a series of axial slots 98located intermediate its inner and outer surfaces. A tooth 100 islocated midway between the ends of each slot 98 which engages with theribs or teeth 70 formed on the bore 72 of the front sleeve member 12 a.The slots 98 provide the flexibility required for the tooth action whilestill maintaining the strength of annulus. In FIGS. 5B-5G furthervariations are shown in the design of the annulus. In FIG. 5B theannulus 64 b is provided with a series of open slots 102 which result ina series of pawls 104 having a tooth 106 at the end thereof whichengages the teeth 70 b on the bore 72 of the front sleeve 12 a. In FIG.5B the tooth 106 has a square profile so that limited torque istransmitted when the sleeve 12 a is rotated in a clockwise directionrelative to the body 16 as viewed in FIG. 5B but unlimited torque istransmitted with counterclockwise rotation. This difference is due tothe asymmetrical shape of the tooth 70 b. FIG. 5C is similar to FIG. 5Bexcept that the tooth 108 has a round rather than a square shape and therear face of the tooth 70 c has correlative shape. FIG. 5D is likewisesimilar to FIG. 5B except that the tooth 110 has a triangular ratherthan a square shape and the tooth 70 d has a correlative asymmetricshape.

[0044] FIGS. 5E-5G show modifications of the structures respectivelyshown in FIGS. 5B-5D. In these modifications the tooth 70 e, 70 f, or 70g is designed to be substantially symmetrical about a radius of thefront sleeve 12 a so that the tightening torque and the loosening torqueare substantially equal. It will be understood that the torquetransmitted through the mechanism is principally a function of the angleof the surface of the teeth 70 and 68, 100, 106, 108 or 110, thecoefficient of friction between the teeth, the force required to depressor deform the teeth 68, 100, 106, 108 or 110, and the number of teeth incontact. The torque increases as the tooth surface approaches a radiusof the front sleeve, as the coefficient of friction increases, as thestiffness of the teeth on the annulus 64 increases, and as the number ofteeth in contact increases. By appropriately controlling thesevariables, the desired tightening and loosening torque may bepredetermined.

[0045] Reference is now made to FIGS. 7 and 8 which show an embodimentof the present invention which is particularly adapted for manualoperation. Again, parts which are substantially the same as in theearlier embodiments bear the same designations while modified parts aredesignated by “a” or “b.” The embodiment of FIG. 7 is characterized bythe location of the torque limiting mechanism in the rear sleeve member14 a. The basic structure of the body member 16, the jaws 18, and thesplit nut member 38 upon which the front sleeve member 12 b is pressedis similar to that shown in FIG. 2 except that a grip boot 74 a isapplied to the surface of the front sleeve member 12 b to enhance thegrippability of the sleeve member. Grip boot 74 a does not provide thetool holding feature shown in FIG. 4 but it is apparent that thisfeature could be added, if desired. The arrangement of bearing 48 andbearing thrust ring 50 a is also similar to that shown in FIGS. 2 and 4except that no serrations or teeth are formed on the outer periphery ofthe bearing thrust ring 50 a. In the embodiment of FIG. 7, the bore 60 ais sized for a sliding fit with the bearing thrust ring 50 a andaccommodates a Belleville or other form of compression spring 112 whichbiases the rear sleeve member 14 a toward a back plate 114 which ispress fitted onto the tail section 22 of the body member 16. As shown inFIG. 8, the back plate 114 may be provided with a plurality of teeth 116and the rear sleeve member 14 a provided with a plurality of radial ribs118. It will be appreciated that during a chucking operation the rearsleeve 14 a will be held while the front sleeve 12 b is turned in aclockwise direction as viewed from the jaw end of the chuck. At apredetermined torque, the ribs 118 will ride over the teeth 116 whilethe rear sleeve 14 a is displaced in a forward direction against thebias of the spring 112. The teeth 116 on the back plate 114 are designedto produce a limited tightening torque and an unlimited looseningtorque. By varying the angle of the teeth faces and the spring rate ofthe compression spring 112 the tightening and loosening torque may bevaried as desired and as explained above. Of course, the teeth 116 andthe ribs 118 may be interchanged, if desired, and various shapes ofteeth may be employed as suggested in FIGS. 5-5G.

[0046] The chuck in accordance with the present invention has a numberof advantages with respect to the ease and cost of manufacture. The bodymember 16 may be machined from a relatively small diameter bar since thebearing thrust ring 50 is made separately and then pressed onto the bodymember. This reduces the machining costs for the body member. Certainparts, such as the split nut and bearing thrust ring may be formed frompowdered metal or stamped or otherwise cold formed with limitedmachining steps. With this design of the load-bearing parts, the moremassive front and rear sleeves may be formed from structural plasticmaterials thereby reducing weight and manufacturing costs whileproviding the ability to customize the chuck through the use of colors,rib shapes, knurling, or identification logos.

[0047] The terms and expressions which have been employed are used asterms of description and not of limitation and there is no intention inthe use of such terms and expressions of excluding any equivalents ofthe features shown and described or portions thereof, but it isrecognized that various modifications are possible within the scope ofthe invention claimed.

What is claimed:
 1. A chuck for a manual or powered driver having arotatable drive shaft, said chuck including: a body, said body includinga front section and a rear section; a plurality of jaws operativelyassociated with said body, said jaws being adapted to engage a tool tobe utilized by the driver; serrations disposed circumferentially about,and rotationally fixed with respect to, and extending outwardly awayfrom, said rear section of said body; and a sleeve member pressed ontosaid serrations whereby said serrations dig into said sleeve to at leastassist in rotationally securing said sleeve to said body.